U.S. patent application number 13/355604 was filed with the patent office on 2013-07-25 for knee brace.
The applicant listed for this patent is Andrew W. Carvey, Mathew Carvey, Philip P. Carvey, Nicholas S. Howard, John A. Rokosz. Invention is credited to Andrew W. Carvey, Mathew Carvey, Philip P. Carvey, Nicholas S. Howard, John A. Rokosz.
Application Number | 20130190669 13/355604 |
Document ID | / |
Family ID | 48797797 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130190669 |
Kind Code |
A1 |
Rokosz; John A. ; et
al. |
July 25, 2013 |
Knee Brace
Abstract
Disclosed and claimed herein is an improved leg brace having a
thigh frame, a shank frame, a knee assembly rotatably coupling the
thigh frame to the shank frame, and a shoe component attached to
the shank frame; the knee assembly having a spring, clutch, means
for engaging the clutch; and programmable means for engaging the
clutch at a selected angle between the thigh frame and shank
frame.
Inventors: |
Rokosz; John A.; (Belmont,
MA) ; Carvey; Philip P.; (Bedford, MA) ;
Howard; Nicholas S.; (Bedford, MA) ; Carvey; Andrew
W.; (Cambridge, MA) ; Carvey; Mathew;
(US) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rokosz; John A.
Carvey; Philip P.
Howard; Nicholas S.
Carvey; Andrew W.
Carvey; Mathew |
Belmont
Bedford
Bedford
Cambridge |
MA
MA
MA
MA |
US
US
US
US
US |
|
|
Family ID: |
48797797 |
Appl. No.: |
13/355604 |
Filed: |
January 23, 2012 |
Current U.S.
Class: |
602/16 |
Current CPC
Class: |
A61F 2005/0155 20130101;
A61F 5/0125 20130101; A61F 2005/0158 20130101; A61F 2005/0179
20130101; A61F 2005/0188 20130101 |
Class at
Publication: |
602/16 |
International
Class: |
A61F 5/00 20060101
A61F005/00 |
Claims
1. An improved leg brace having a thigh frame, a shank frame, a
knee assembly rotatably coupling the thigh frame to the shank
frame, and a shoe component attached to the shank frame; the knee
assembly having a spring, clutch, and means for engaging the
clutch; the improvement comprising: programmable means for engaging
the clutch at a selected angle between the thigh frame and shank
frame.
2. The leg brace of claim 1, further comprising: a second knee
assembly configured so that, when in use, one knee assembly is on
the medial side of the leg and the other knee assembly is on the
lateral side of the leg.
3. The leg brace of claim 1, further comprising: programmable means
for releasing the clutch at a selected angle between the thigh
frame and shank frame.
4. The leg brace of claim 1, wherein the clutch is a one-way
clutch.
5. The leg brace of claim 1, further comprising means for
programming the maximum permitted tibiofemoral joint forces during
knee flexion.
6. The leg brace of claim 1, further comprising a command module in
wired or wireless communication with the programmable means for
engaging the clutch at the selected angle.
7. The leg brace of claim 1, further comprising automatic means for
adjusting the selected angle wherein the clutch is engaged, during
an extended period of ambulation.
8. The leg brace of claim 1, further comprising programmable means
for situationally adjusting the selected angle wherein the clutch
is engaged.
9. The leg brace of claim 1, further comprising automatic means for
adjusting the selected angle at which the clutch is engaged in
accordance with a training schedule.
10. A leg brace, comprising: a. a shank frame; b. a thigh frame; c.
at least one knee joint, rotatably coupling the shank frame to the
thigh frame; d. at least one non-linear torsion spring having a
torsional axis at the at least one knee joint wherein the torsion
spring hardens with increasing angle of knee flexion; e. at least
one clutch with an input arbor coupled to the at least one
non-linear torsion and an output arbor coupled to: i. the thigh
frame; or ii. the shank frame. f. a programmable controller,
operatively coupled to the at least one clutch, for: i. engaging
the at least one clutch at a selected angle between the thigh frame
and the shank frame in relation to heel strike during ambulation;
and ii. releasing the at least one clutch at a selected angle
between the thigh frame and the shank frame during knee
extension.
11. The leg brace of claim 10, further comprising a command module,
in wired or wireless communication with the programmable
controller, for situationally selecting the angle of knee flexion
at which the at least one clutch is engaged.
12. The leg brace of claim 10, wherein the at least one clutch is a
one-way clutch
13. The leg brace of claim 10, further comprising automatic means
for adjusting the selected angle wherein the clutch is engaged,
during an extended period of ambulation.
14. The leg brace of claim 10, further comprising programmable
means for situationally adjusting the selected angle wherein the
clutch is engaged.
15. The leg brace of claim 1, further comprising automatic means
for adjusting the selected angle at which the clutch is engaged in
accordance with a training schedule.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to orthopedic braces that are
fitted to a patient's leg, knee and foot.
BACKGROUND
[0002] In patients with knee osteoarthritis, as the tibiofemoral
forces increase, knee pain can increase significantly. It is
therefore of value to reduce the tibiofemoral forces on the knee
joint during ambulation over a variety of surfaces and
terrains.
[0003] A number of orthotic devices have been designed to reduce
tibiofemoral joint forces and alleviate pain associated with joint
movement, and sometimes to rehabilitate the joint over time.
[0004] For example, Nace, in U.S. Pat. No. 8,057,414 discloses and
claims an offloading brace that is designed to relieve pressure on
either the medial or lateral side of the tibiofemoral joint. In
addition, there is employed a "spring loaded adjustable fulcrum" to
assist in leg extension after the knee is flexed. However, while
different amounts of spring torque may be introduced by adjusting
the mechanical spring settings before the brace is donned, there
are no means for modifying the spring torque while being worn or
programmably as a function of knee angle. Moreover, there are no
means for locking the spring in compression and releasing the
spring at a selected angle during ambulation.
[0005] As a further example, in U.S. Pat. No. 6,010,474, Wycoki
discloses a leg orthotic device that is said to offload
tibiofemoral forces on the knee joint bilaterally. In addition, the
disclosed orthotic device is said to relieve pressure on the
patellar compartment. There is also disclosed a spring assembly for
"biasing the knee toward extension." The pressure on the knee joint
is said to be offloaded by "transferring the pressure through the
strut assembly to the thigh" using straps and an inflatable thigh
cuff. However, while different amounts of spring thrust at heel
strike may be introduced by adjusting the mechanical spring
settings before the brace is donned, there are no means for
modifying the spring thrust while being worn or programmably as a
function of knee angle. Moreover, there are no means for locking
the spring in compression and releasing the spring at a selected
angle during ambulation.
[0006] In U.S. Pat. No. 7,393,335, Carvey et al., incorporated
herein by reference, disclose a knee brace that provides support
for the torso via the hip and increases leg thrust. However, Carvey
et al. do not provide a method of programmably modifying the torque
from the spring beginning at a programmable angle during knee
flexion and releasing the spring at a programmable angle during
knee extension.
[0007] Therefore, there remains a need for a biomechanical leg
orthosis that, during ambulation, provides a programmable means for
storing energy while the knee is flexing and a means for
programmably releasing the stored energy when the knee is
extending. Moreover, there remains a need for an improved leg
orthosis that begins storing energy at a selected angle of knee
flexion angle after heel strike. These needs are addressed by the
subject matter disclosed and claimed herein.
DETAILED DESCRIPTION
[0008] As used herein, the conjunction "and" is intended to be
inclusive and the conjunction "or" is not intended to be exclusive
unless otherwise indicated. For example, the phrase "or,
alternatively" is intended to be exclusive. As used herein, the
article "a" is understood to mean "one or more." As used herein,
the term "exemplary" is understood to indicate a particular example
and is not otherwise intended to indicate preference. As used
herein, the "knee angle" is understood to be measured by using the
angle between the thigh frame and the shank frame of the leg brace
in circumstances where the leg brace is being worn. Herein, "knee
flexion" is understood as the act of bending the knee joint.
Herein, "knee extension" is understood as the act of straightening
the knee joint. It is further understood that the knee joint can be
hyperextended beyond its normal straightened position.
[0009] Disclosed and claimed herein is an improved leg brace having
a thigh frame, a shank frame, a knee assembly rotatably coupling
the thigh frame to the shank frame, and a shoe component attached
to the shank frame; the knee assembly having a spring, a clutch,
and means for engaging the clutch; the improvement comprising:
programmable means for engaging the clutch at a selected angle
between the thigh frame and shank frame.
[0010] Further disclosed and claimed herein is a leg brace, having:
a shank frame for transferring forces between a wearer's
tibia/fibula and the shank frame; a thigh frame for transferring
forces between a wearer's femur and the thigh frame; at least one
knee joint for rotatably coupling the shank frame to the thigh
frame; at least one non-linear torsion spring having a torsional
axis at the at least one knee joint wherein the torsion spring
hardens with increasing angle of knee flexion; at least one clutch
with an input arbor coupled to the at least one non-linear torsion
spring and an output arbor coupled to the thigh frame or the shank
frame; a programmable controller, operatively coupled to the at
least one clutch, for engaging the at least one clutch at a
selected angle in relation to the heel strike during ambulation,
whereby a reduction of tibiofemoral forces results; and releasing
the at least one clutch at a selected angle during knee
extension.
[0011] The leg brace disclosed and claimed herein may further
comprise a second knee assembly, configured so that, when in use,
one knee assembly is on the medial side of the leg and the other
knee assembly is on the lateral side of the leg. This arrangement
may be particularly useful in situations where bicompartmental
relief of pressure on the tibiofemoral joint is desired.
[0012] The leg brace disclosed and claimed herein may further
comprise programmable means for releasing the clutch at a selected
angle between the thigh frame and shank frame. When wearing the leg
brace while ambulating, kinetic energy is converted into strain
energy and stored in the spring during knee flexion. Thus,
releasing the spring clutch during knee extension converts the
stored energy back into kinetic energy and further provides support
for the quadriceps muscle group in circumstances where one or more
of the quadriceps muscles are weakened by, for example injury or
nonuse.
[0013] The leg brace disclosed and claimed herein may comprise a
one-way clutch in the knee assembly, configured to have an
orientation selected such that its free direction of rotation
occurs during the wearer's knee flexion.
[0014] The leg brace disclosed and claimed herein may further
comprise means for programming the maximum permitted tibiofemoral
joint forces during knee flexion.
[0015] The leg brace disclosed and claimed herein may further
comprise a command module in wired or wireless communication with
the programmable means for engaging the clutch at the selected
angle.
[0016] The leg brace disclosed and claimed herein may further
comprise automatic means for adjusting the selected angle, wherein
the clutch is engaged, during an extended period of ambulation.
This may be useful, for example, in the training or therapy of the
braced leg.
[0017] The leg brace disclosed and claimed herein may further
comprise programmable means for situationally adjusting the
selected angle wherein the clutch is engaged. Such a program may be
used, for example, in accordance with leg strength training
goals.
[0018] The leg brace of claim 1, further comprising automatic means
for adjusting the selected angle wherein the clutch is engaged, in
accordance with usage history. In this circumstance, for example,
the controller may be programmed to increase the selected angle
wherein the clutch is engaged in order to require more quadriceps
involvement and less assistance from the brace.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows a side view of a person wearing an embodiment
of the present invention.
[0020] FIG. 2 shows a mechanical schematic diagram of the
mechanical portion of the present invention.
[0021] FIG. 3A shows the simulated normalized tibiofemoral joint
force as a function of knee angle for an unassisted knee. FIG. 3B
shows simulated thigh assist force as a function of knee angle,
delivered by an embodiment of this invention at seven assistance
levels. FIG. 3C shows simulated normalized tibiofemoral total force
versus knee angle for seven levels of knee brace assistance.
[0022] FIG. 4 shows a perspective view of a person employing the
embodiment of FIG. 1 on both legs and a command module on the
wrist.
[0023] FIG. 5 shows a side view with a torsion spring and
clutch.
[0024] FIG. 6 is a block diagram showing an embodiment of an
electronics control module.
[0025] FIG. 7 is a block diagram of an embodiment of control logic
that may be implemented in the electronics control module.
DETAILED DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 shows a schematic side view of a person wearing one
embodiment of the present invention. The general brace includes a
shank frame 2, a thigh frame 3 and a knee assembly rotatably
coupling the thigh frame to the shank frame 11 wherein is mounted a
nonlinear torsion spring assembly, discussed infra. An alternate
embodiment includes a shoe component 1 attached to the shank frame
2 for attaching to a wearer's shoe 4. Not shown are sensors for
measuring the pressure and weight on the heel and other points on
the bottom of the foot. Thigh frame 3 includes a thigh strap 5 and
a padded thigh shell 6 for providing a means for coupling the force
on the back of the thigh, F.sub.thigh,7 between the wearer's femur
and the thigh frame 3. The shank frame 2 includes a shank strap 8
and a padded shank shell 9 for providing a means for coupling force
at the front of the shank, F.sub.shank10 between the wearer's tibia
and the shank frame 2.
[0027] The knee assembly rotatably coupling the thigh frame to the
shank frame 11 includes a spring (not shown) that, when compressed,
produces a torque, T.sub.k 12 between the thigh frame 3 and the
shank frame 2. The magnitude of T.sub.k 12 is dependent on the
compression angle of the spring .sigma..sub.k-.sigma..sub.e, where
.sigma..sub.e (not shown) is the selected knee angle at which the
spring is engaged. The knee angle .sigma..sub.k shown at 13. Forces
F.sub.ankle1 14 and F.sub.ankle2 15 are forces applied by the shoe
component attached to the shank frame 1 to the shank frame 2 at an
ankle joint 16. F.sub.hip 17 is a force applied by the torso to the
hip socket caused by the gravitational field and inertial forces.
Accordingly, as an approximation, F.sub.hip 17 has a direction
pointing directly from hip socket 18 to ankle joint 16. The only
direct coupling between ground reaction force (GRF) and the
wearer's hip socket 18 is through the wearer's foot, tibia and
femur. The brace, however, provides an indirect coupling assistance
force F.sub.S between the GRF and the wearer's hip socket 18,
pointing directly from ankle joint 16 to hip socket 18, with
magnitude that increases from zero to its maximum value as a
function of the knee angle .sigma..sub.k 13.
[0028] FIG. 2 shows a mechanical schematic diagram of the knee
assembly. One or more knee assemblies 51 and 53-55 rotatably
couples the thigh frame 50, and shank frame 52. A hinge 51 is
operatively coupled to a spring 54, which is controlled by an inner
spring clutch 53 and an outer clutch 55. The spring 54, the inner
spring clutch 53 and the outer clutch 55 are shown in operable
contact with a drum 56. It should be understood that a brace as
described herein may comprise one or more knee assemblies, for
example, on the medial or lateral sides of the knee.
[0029] FIG. 3A shows the normalized tibiofemoral joint force versus
knee angle (the angle between the thigh frame and the shank frame)
for an unassisted leg assuming a constant patella tendon to knee
axis separation distance. For the stance leg, the torque on the
knee created by the torso weight plus swing leg has to equal the
torque on the knee generated by the stance leg quadriceps muscle so
that the normalized tibiofemoral force for the unassisted leg
during the stance phase is given by:
F tf ( k ) = 1 + L thigh L pk sin ( k 2 ) .about. 1 + 10 sin ( k 2
) ##EQU00001##
Wherein .sigma..sub.k denotes the knee angle, L.sub.thigh denotes
the length of the thigh, L.sub.pk denotes the patella tendon to
knee axis separation distance, the length ratio is approximately
equal to 10 and the actual force may be calculated by multiplying
the normalized tibiofemoral joint force by the weight of the torso
plus the weight of the swing leg.
[0030] A unity value on the Y scale represents approximately 83% of
bodyweight (torso weight plus weight of swing leg). For a knee
angle of zero, the normalized tibiofemoral force equals unity. As
the knee angle increases, the tibiofemoral force increases
approximately 10
sin ( k 2 ) ##EQU00002##
from unity to about six at a knee angle of 65.degree..
[0031] FIG. 3B shows plots of the simulated normalized assistance
force (NAF) as a function of the angle between the thigh frame and
the shank frame. Seven different curves corresponding to different
angles of clutch engagement are shown at 2.degree. increments
40-46. The curve labeled 40 is at the reference clutch engagement
angle of 0.degree., wherein the maximum level of NAF is experienced
by the user. Smaller levels of NAF are experienced by the user as
the angle of clutch engagement is increased from 2.degree. to
12.degree. as shown in curves 41-46. For a particular nonlinear
spring, the assistance force is given by:
F s = .tau. s L thigh sin ( k 2 ) = [ k 1 ( k - e ) ( 1 + k 2 ( k -
e ) ) ] L thigh sin ( k 2 ) = F s ( k - e ) ##EQU00003##
[0032] Wherein the assistance force is computed as the ratio of the
torque on the spring .tau..sub.s to the length of the thigh,
L.sub.thigh. The constants k.sub.1 and k.sub.2 may be obtained by
fitting to the experimental data or by other equivalent means. The
spring compression angle, denoted by (.sigma..sub.k-.sigma..sub.e),
is the difference between the knee angle, .sigma..sub.k, and the
angle at which the clutch engages, .sigma..sub.e. The assistance
force, F.sub.s (.sigma..sub.k-.sigma..sub.e), is thus a function of
the spring compression angle. In the above, the function shown is
not intended to be limiting but may take a number of reasonable
forms, particularly if adjustable parameters are used. The
function, F.sub.s(.sigma..sub.k-.sigma..sub.e), may be further
interpolated and extrapolated using polynomials, spline functions,
rational functions, normalized spectral elements and equivalents
thereof or combinations thereof. Further, table lookup logic may
comprise ordered table searching, searching with correlated values,
estimation by neural networks, multidimensional estimation,
equivalents thereof or combinations thereof.
[0033] FIG. 3C shows plots of the simulated normalized tibiofemoral
force (NTF) as a function of the angle between the thigh frame and
the shank frame for the assisted leg. Seven different curves
corresponding to the angle of clutch engagement are shown at
2.degree. increments 30-36. The curve labeled 30 is at the
reference angle of 0.degree., wherein the minimum level of NTF is
experienced by the user. This reference angle represents the
maximum support from the brace (the maximum normalized assistance
force (NAF)) when the clutch is engaged prior to or at heel strike.
Greater levels of NTF are experienced by the user as the angle of
clutch engagement is increased from 2.degree. to 12.degree. as
shown in curves 31-36. In one embodiment, the assisted tibiofemoral
force may be computed in the following way:
F tf ( k , e ) = 1 + ( 1 - F s ( k - e ) ) sin ( k 2 ) for k
.gtoreq. e and F s ( k - e ) < 1 ##EQU00004##
Where F.sub.tf(.sigma..sub.k, .sigma..sub.e) is the normalized
tibiofemoral force and .sigma..sub.k, .sigma..sub.e,
F.sub.s(.sigma..sub.k-.sigma..sub.e), L.sub.thigh, L.sub.pk are all
as defined above. Without limitation, the condition
.sigma..sub.k.gtoreq..sigma..sub.e may be applied optionally.
However, it is also contemplated that support for knees in the
hyperextended condition may require spring response that is defined
for .sigma..sub.k.ltoreq..sigma..sub.e. Moreover, the range of
defined spring compression may vary. In one embodiment, the range
through which spring compression is defined may be
-10.degree.-60.degree.. In another embodiment, the range through
which spring compression is defined may be -5.degree.-50.degree..
In still another embodiment, the range through which spring
compression is defined may be 0.degree.-45.degree.. It may be
convenient to define a "zero" of knee angle, .sigma..sub.k, as a
reference. This angle may be that at which the heel, the knee joint
and the hip joint are all approximately collinear or at another
angle of knee flexion.
[0034] FIG. 4 shows a perspective view of a person employing the
embodiment of FIG. 1 on both legs. Each brace includes a shank
frame 2, a shoe component attached to the shank frame 1, a thigh
frame 3, at least one knee assembly rotatably coupling the thigh
frame to the shank frame 11, and a control module 25, wherein are
contained electronic components for the programmable means for
engaging and releasing the clutch at selected angles as measured
between the thigh frame and shank frame. Optionally, a command
module 20 can be used in wired or wireless communication with the
programmable means for engaging the clutch at the selected angle.
The command module 20, may be used situationally to adjust
settings. Shown in FIG. 4 are leg braces employing two knee
assemblies for rotatably coupling the thigh frame to the shank
frame, respectively on the lateral and medial sides of the knee.
However, an embodiment of a brace having one knee assembly is also
contemplated. Moreover, although a pair of braces is shown, it
should be understood that a single brace on one leg can be
employed.
[0035] FIG. 5 shows a side view of one embodiment of a knee
assembly 11 (FIG. 1) coupled to the thigh frame 3 (FIG. 1) and the
shank frame 2 (FIG. 1). The knee assembly 11 includes a thigh
clutch assembly, a spring clutch assembly, a transfer arbor
assembly, and a torsion spring 70. The thigh clutch assembly
includes a thigh clutch wire 73 (at output arbor of the thigh
clutch) and a thigh clutch actuator 75. The thigh clutch assembly
is a mechanism for transferring torque from the thigh frame 3 (FIG.
1) to the transfer arbor under microprocessor control. The spring
clutch assembly includes a spring clutch wire 74 (at output arbor
of the spring clutch) and a spring clutch actuator 76. The spring
clutch assembly is a mechanism for transferring torque from one arm
of the torsion spring to its other arm under microprocessor
control. The transfer arbor assembly includes two side plates (not
shown), a thigh clutch arbor 71 (at input arbor of the thigh
clutch), a spring clutch arbor 72 (at the input arbor of the spring
clutch), and a transfer arbor pin 83. Knee axle 84 provides a means
for the shank frame 2, thigh frame 3, and the transfer arbor to
rotate around a single axis of rotation.
[0036] The thigh frame 3 includes a thigh frame side strut 77, a
thigh frame side plate 78, and a thigh wire termination 79 that are
fixed relative to one another. The shank frame 2 includes a shank
frame side strut 80, a shank frame side plate 81, a torsion arm pin
82 that and are fixed relative to one another. One arm of the
torsion spring is directly coupled to the shank frame 2 (FIG. 1)
via the torsion arm pin 82 while the other arm of the torsion
spring 70 is directly coupled to the thigh clutch arbor 71 via
transfer arbor pin 83. The thigh frame 3, the shank frame 2, and
the transfer arbor all rotate around a common axis of rotation.
Stops prevent hyperextension of the knee joint and limit flexion of
the knee to approximately 130.degree..
[0037] Programmable means for engaging the clutch at the selected
angle and releasing the clutch at the most propitious time may be
provided in hardware, software or a combination. FIG. 6 is an
embodiment of a block diagram of an electronics control module.
Control of the brace is accomplished by a program resident within a
microprocessor 161. The output voltages of four angle sensors are
routed directly to A-D inputs of the microprocessor 161. The
signals produced by three pressure pad preamplifiers within the
brace (not shown), are amplified, rectified and filtered in
pressure pad amplifier/filters 163. A dual axis accelerometer 164
allows measurement of the acceleration on the shank frame 2 (FIG.
1) over a selected acceleration range. An exemplary acceleration
range is +/-2.0 G. Another exemplary acceleration range is +/-1.5
G. Still another exemplary acceleration range is +/-1.0 G. An
exemplary tolerance for the measured acceleration is one part in
5000. A further exemplary tolerance for the measured acceleration
is 1 part in 1000. A still further exemplary tolerance for the
measured acceleration is one part in 500. The accelerometer is
employed both to detect heel strike and to sense the shank frame 2
orientation relative to the earth's gravitational field. A command
module 165 and 20 (FIG. 4) in wired or wireless communication with
the programmable means for engaging the clutch at the selected
angle allows the wearer to enter commands to the electronics module
during configuration and situationally. A pulse width modulated
(PWM) current limited thigh motor driver 166 is employed to drive
the motor within the thigh clutch actuator 75 (FIG. 5). The driver
provides a means for the microprocessor to drive the motor in both
directions. A PWM current limited spring motor driver 167 is
employed to drive the motor within the spring clutch actuator 76
(FIG. 5). The microprocessor 161 may also drive other devices such
as LED indicator lights, one or more displays, speakers and the
like. Further included but not shown may be a keyboard for local
programming, communication equipment for remote programming and
telemetric monitoring and memory storage for storing the usage data
for later analysis and programs for training exercises, adjusting
the brace for extended periods of ambulation and adjusting the
brace for other situations encountered during use.
[0038] Wired communication may be accomplished via digital or
analog methods in a variety of serial or parallel formats. Wireless
communication may be accomplished via Bluetooth, WiFi, infrared
signals or the equivalent. Such commands can be issued from a wrist
module 20, a sequence of pressures applied to the pressure pads in
a sensorized shoe insole, a keyboard, or biometric indicators such
as voice, eye movement, finger arm or wrist movement, equivalents
thereof or combinations thereof.
[0039] In this embodiment, a pulse width modulated (PWM) current
limited thigh CAM motor driver 166 is employed to drive the motor
within the thigh clutch actuator 75 (FIG. 5). The driver provides a
means for the microprocessor to drive the motor in both directions.
A PWM current limited spring CAM motor driver 167 is employed to
drive the motor within the spring clutch actuator 76 (FIG. 5). The
microprocessor 161 may also drive other indicators such as LEDs,
displays, speakers, wireless devices such as Bluetooth, WiFi,
infrared or the equivalent. In this embodiment uses two
motor/gearbox driven CAMs 166 and 167 to supply a force to the
control side of each of the clutches. In normal operation, the CAM
makes one revolution for each step cycle. The control CAM has an
engineered shape such that the control force can be varied from
zero to maximum over any time period and the force can be changed
from maximum to zero almost instantaneously. The shape of the CAM
may further be designed to minimize the power drain from the
battery.
[0040] FIG. 7 shows a diagram of the control logic used to select
the angle of clutch engagement and release and to actuate and
release a clutch. In this embodiment, it is assumed for simplicity
that status monitoring is done continually and that monitored
parameter information is fetched or otherwise made available when
required. Further, for simplicity, it is assumed that redundant
commands are ignored. For example, a command to release an already
released clutch is ignored. Further, it is understood herein that
collinear control lines are presumed to function independently.
[0041] As shown in FIG. 7, at some point during ambulation, the leg
is in its swing phase, as depicted in control module 100, wherein
the knee joint is being extended and the knee clutch is disengaged.
There is negligible pressure on the bottom of the foot, the spring
is not compressed and the spring compression angle is defined as
zero under this condition. During the swing phase, heel forces are
monitored to determine whether heel strike has occurred as shown in
decision point 101. In this embodiment, the system is looped
between control module 100 and decision point 101 until heel strike
occurs.
[0042] Heel strike is detected by pressure sensors at the bottom of
the foot 163 (FIG. 6) Heel strike is confirmed by accelerometer 164
(FIG. 6) and/or a tilt sensor (not shown) and control is passed to
status block 102 where the knee angle (the angle between the shaft
frame and thigh frame) is measured and tested at decision point 103
to determine whether the target angle for clutch engagement has
been reached. During knee flexion, tibiofemoral forces increase as
torso weight is shifted onto the braced leg. Pressure sensors on
the sole of the foot measure the pressure as the knee undergoes
flexion. Once the target angle is reached, control is passed to
routine 104, which issues a command to engage the knee clutch.
[0043] Control is then passed to decision point 105, which tests
whether the spring is compressing (increasing spring angle) or is
decompressing (decreasing spring angle). Increases in the
tibiofemoral force are limited by further compression of the spring
as weight continues to be shifted onto the brace. If the spring
angle rate of change is positive, the knee clutch remains engaged;
control returns to 104 which passes control to decision point 105.
If the spring angle rate of change is negative, control is passed
to decision point 106 which tests whether the knee angle has
reached its prescribed value for clutch release e.g. the spring
compression angle has reached a value of zero.
[0044] Control is looped between decision points 105 and 106 until
the prescribed clutch release knee angle is reached. Once the
release angle is reached, control is passed to control module 107
which releases the knee clutch, allowing the knee to rotate
freely.
[0045] Control is then passed to decision point 108, which tests
continually whether the leg is in swing phase. If the leg is in
swing phase, control is passed to control module 100. If the leg is
not in swing phase, control is passed to decision point 109, which
tests whether the angle between the thigh frame and the shank frame
is decreasing with time. If the leg brace angle is decreasing,
control is passed to control module 104, which engages the knee
clutch and computes or obtains from memory the clutch release
angle. If the leg brace angle is increasing or stationary, control
is passed to control module 107.
[0046] It should be understood that status monitoring and control
of parameters such as angles, forces, for example at heel strike,
spring direction, and rates of change may be accomplished in-line
or continually by means of interrupt service routines, direct
memory access, adaptive interrupt systems, multiprocessor
environments and the like. Further, interrupts and direct memory
access events can be masked and/or prioritized when required.
Communication with the processor can be accomplished by various
means known in the art, for example, parallel communication, serial
communication, communication via a universal serial bus, firewire
and the like. Further, various wireless technologies may be
employed such as WiFi, ZigBee, infrared, Bluetooth and the like.
Communication methods can be point-to-point or broadcast to all
points, wherein, at each point of contact, irrelevant signals are
discarded.
[0047] Different types of clutch may be used. Without limitation,
these can include centrifugal clutches, cone clutches, torque
limiting clutches, hydraulic clutches, electromagnetic clutches,
freewheel clutches, ratchet clutches wrap spring clutches and the
like. Further, clutches employed as described herein may be one-way
clutches. One-way clutches transmit torque in one rotational
direction while stopping torque in the opposite direction. In one
embodiment, both a microprocessor activated thigh clutch and spring
clutch are used during normal operation. Both clutches are one-way
dual-state clutches. In many embodiments, there is an input arbor
and an output arbor and a means for coupling torque between input
arbor and output arbor. In dual-state clutches, there are two
states in which the clutch is either released or actuated. In its
released state, negligible torque is transferred from the input
arbor to the output arbor before slippage occurs. In the actuated
state, a large torque is coupled from input arbor to output arbor
before slippage occurs. Transition between states may be effected
either mechanically or electrically typically via a solenoid.
[0048] Operation of a one-way dual-state clutch (employed in an
embodiment of the invention) is similar to a dual-state clutch in
the released state. In the actuated state, operation of the one-way
dual-state clutch differs because large amounts of torque can be
transferred from input arbor to output arbor only in one rotational
direction, called the "hard" direction. When in the actuated state,
only a small amount of torque is transferred from input arbor to
output arbor before slippage occurs in the other direction, called
the "easy" direction. Note that in any physical implementation of a
one-way dual-state clutch, the maximum torque transferable between
the input arbor and the output arbor without slippage is limited by
the physical parameters of the clutch. Moreover, the easy direction
torque will normally be much larger than release state transfer
torque.
[0049] In accordance with the above referenced drawings and the
accompanying description, means for engaging the clutch may
comprise an assembly of pressure sensors, angle sensors, one or
more accelerometers, actuators processors, auxiliary circuits,
program logic, equivalents thereof or combinations thereof.
[0050] In accordance with the above referenced drawings and the
accompanying description, programmable means for engaging the
clutch at a selected angle between the thigh frame and shank frame
may comprise an assembly of pressure sensors, angle sensors, one or
more accelerometers, actuators processors, auxiliary circuits,
program logic, equivalents thereof or combinations thereof.
[0051] In accordance with the above referenced drawings and the
accompanying description, programmable means for releasing the
clutch at a selected angle between the thigh frame and shank frame
may comprise an assembly of pressure sensors, angle sensors, one or
more accelerometers, actuators processors, auxiliary circuits,
program logic, equivalents thereof or combinations thereof.
[0052] In accordance with the above referenced drawings and the
accompanying description, means for programming the maximum
permitted tibiofemoral joint forces during knee flexion may
comprise an assembly of pressure sensors, angle sensors, one or
more accelerometers, actuators processors, auxiliary circuits,
table lookup logic, program logic, equivalents thereof or
combinations thereof. For example, in circumstances where the user
can tolerate a tibiofemoral force corresponding to a normalized
value of 1.6, the microprocessor of FIG. 6 may be programmed to
provide more assistance from the leg brace by adjusting the angle
of clutch engagement to occur at about 6.degree.. If even more
support is required, the angle of clutch engagement can occur at
0.degree. (heel-strike), so that the maximum normalized
tibiofemoral force reaches a value of only about 1.1. Angle values
can be incorporated into program logic by using any of the methods
of interfacing discussed herein.
[0053] In accordance with the above referenced drawings and the
accompanying description, automatic means for adjusting the
selected angle wherein the clutch is engaged, during an extended
period of ambulation may comprise an assembly of pressure sensors,
angle sensors, one or more accelerometers, actuators processors,
auxiliary circuits, table lookup logic, program logic, equivalents
thereof or combinations thereof. For example, in circumstances
where the user experiences fatigue during ambulation, the
microprocessor of FIG. 6 may be programmed to provide more
assistance from the leg brace by incrementally providing more
support to the tibiofemoral joint by incrementally decreasing the
angle at which the clutch is engaged over the course of the walk,
in accordance with FIG. 3C. If clutch engagement occurs at an angle
of 12.degree., for example, the maximum normalized tibiofemoral
force reaches a value of about 2.1. If clutch engagement occurs at
an angle of 6.degree., the maximum normalized tibiofemoral force
reaches a value of about 1.6. On the other hand, if clutch
engagement occurs at an angle of 0.degree. (heel-strike), the
maximum normalized tibiofemoral force reaches a value of only about
1.1 as the brace supplies more stored energy from the spring. Angle
values can be incorporated into program logic by using any of the
methods of interfacing discussed herein.
[0054] In accordance with the above referenced drawings and the
accompanying description, means for situationally adjusting the
selected angle wherein the clutch is engaged, may comprise an
assembly of pressure sensors, angle sensors, one or more
accelerometers, actuators processors, auxiliary circuits, table
lookup logic, program logic, a command module carried or worn by
the user, equivalents thereof or combinations thereof. The command
module may be configured to monitor various bodily functions such
as electrocardiogram signals heart rate, perspiration, body
temperature, blood pressure, oxygen level and the like. A wired or
wireless communications module can be used to program the
microprocessor of FIG. 6 to reduce the exertion of the muscles in
the braced leg upon command. For example, in circumstances where
measurements indicate a low blood oxygen level, the microprocessor
of FIG. 6 may be programmed to provide more assistance from the leg
brace by decreasing the angle at which the clutch is engaged, in
accordance with FIG. 3C. In this example, if clutch engagement
occurs at an angle of 6.degree., the maximum normalized
tibiofemoral force reaches a value of about 1.6. In response to a
lower oxygen level, the, clutch engagement could be reduced to an
angle of 0.degree. (heel-strike), the maximum normalized
tibiofemoral force reaches a value of only about 1.1 as the brace
supplies more stored energy from the spring. In addition,
quadriceps involvement during the swing phase decreases to a
negligible value. Clutch engagement angle values can be programmed
situationally as inputs to the controlling program logic by using
any of the methods of interfacing discussed herein.
[0055] In accordance with the above referenced drawings and the
accompanying description, automatic means for adjusting the
selected angle at which the clutch is engaged in accordance with a
training schedule may comprise an assembly of pressure sensors,
angle sensors, one or more accelerometers, actuators processors,
auxiliary circuits, table lookup logic, program logic, a command
module carried or worn by the user, equivalents thereof or
combinations thereof. In addition, a training schedule can be
incorporated into the microprocessor so that the angle of clutch
engagement is varied in accordance with the amount of tibiofemoral
force and quadriceps involvement. The training module can be
programmed to increase the angle of clutch engagement over days,
weeks or months or the angle of clutch engagement can be varied
according to whether certain physiological targets are achieved.
The command module may be configured to monitor various
physiological parameters such as electrocardiogram signals heart
rate, perspiration, body temperature, blood pressure, oxygen level
and the like. A wireless communications module, such as a Zigbee
radio module, can be used to program the microprocessor of FIG. 6
to change the exertion of the muscles in the braced leg upon
command. For example, in circumstances where a target heart rate is
desired, the microprocessor of FIG. 6 may be programmed to provide
less assistance from the leg brace by increasing the angle at which
the clutch is engaged, and then provide a level of assistance
designed to maintain the desired heart rate by decreasing or
increasing the angle as required to maintain the desired heart
rate. The level of assistance from the brace can thus be adjusted
upward or downward by adjusting the clutch engagement angle. Clutch
engagement angle values can programmed situationally as inputs to
the controlling program logic by using any of the methods of
interfacing discussed herein.
[0056] Pressure sensors may comprise piezoelectric sensors,
piezoresistive sensors, capacitive sensors, which may comprise
foams or other elastic materials as well as ceramics and fluids,
electromagnetic sensors, in which the physical displacement of a
diaphragm or cantilever causes changes in inductance, reluctance or
capacitance, a linear variable differential transformer device,
Hall effect device, equivalents thereof or combinations
thereof.
[0057] Angle sensors may comprise accelerometers, liquid capacitive
inclinometers, electrolytic inclinometers, gas bubble in liquid
devices, pendulum devices, giant magnetoresistive sensors,
potentiometric sensors, Hall effect sensors, anisotropic
magnetoresistive sensors, optical encoders, equivalents thereof or
combinations thereof.
[0058] Accelerometers may comprise piezoresistive sensors,
piezoelectric sensors, moving mass sensors, giant magnetoresistive
sensors, anisotropic magnetoresistive sensors, capacitive sensors,
resonant beam sensors, vibrating cantilever sensors, force balance
sensors, transducer electronic data sheet (TEDS) accelerometers,
wireless accelerometers, equivalents thereof or combinations
thereof. Accelerometers may operate in uniaxial, biaxial or
triaxial mode.
[0059] Actuators may comprise optoelectronic devices, CAM devices,
linear motors, voice coils, moving magnetic actuators, amplified
and direct piezoelectric devices, electric motors, pneumatic
actuators, hydraulic pistons, relays, comb drive devices, thermal
bimorphs, digital micromirror devices, electroactive polymers,
screw jack, ball screw and roller screw actuators, hoist, winch,
rack and pinion, chain drive, belt drive, rigid chain and rigid
belt actuators, gear drive actuators, equivalents thereof or
combinations thereof.
[0060] The sensors and actuators described above may be
manufactured as microelectronic nanoelectronic or
microelectromechanical devices, equivalents thereof or combinations
thereof.
[0061] Processors may comprise any circuit for performing data
processing, including digital signal processors, single processors,
parallel processors, analog processors, memory management
processors, optical processors, equivalents thereof and
combinations thereof. In addition, processors may include auxiliary
circuits, either integrated with the processor or in separate
devices operating with the processor. Auxiliary circuits may be any
circuit that provides an additional function on behalf of the
processors and can be shared between two or more processors.
Auxiliary circuits may include memories such as semiconductor
memories, magnetoresistive memories, disk memories, flash memories,
or any equivalent means for storing data, auxiliary circuits may
further comprise gate arrays, adders, other programmed logic
circuits, amplifiers, triggers, A/D converters, D/A converters,
optical interfaces, serial and parallel interfaces, buffers,
masking circuits, encryption circuits, direct memory access
circuits, equivalents thereof or combinations thereof.
[0062] Program logic may comprise computer programs written in any
known language, such as C, C++, Pearl, Fortran, Basic, Pascal,
assembly language, machine language, equivalents thereof or
combinations thereof. Program logic may further comprise parallel
processing logic for employing multiple processors or processor
cores, direct memory access logic for continual monitoring
functionality, masked direct memory access, interrupt routines,
interrupt service routines, equivalents thereof or combinations
thereof.
[0063] Table lookup logic may comprise interpolation and
extrapolation routines, based on polynomials, spline functions,
rational functions, normalized spectral elements, equivalents
thereof or combinations thereof. Further, table lookup logic may
comprise ordered table searching, searching with correlated values,
estimation by neural networks, multidimensional estimation,
equivalents thereof or combinations thereof. Data for table lookup
may be obtained experimentally, using the brace and electronics
described herein. Further, data such as that shown in FIG. 3C may
be obtained by simulation that incorporates the biomechanics of the
braced leg in accordance with the forces and angles depicted in
FIG. 1.
[0064] Although the present invention has been shown and described
with reference to particular examples, various changes and
modifications which are obvious to persons of ordinary skill in the
art to which the invention pertains are deemed to lie within the
spirit, scope and contemplation of the subject matter as set forth
in the appended claims.
* * * * *